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COS-11D SMQV transmitters gain issues


Laurence T
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11 hours ago, Laurence T said:

I had exposed the connecter and have found the following. Could anyone perhaps tell me if this is correct? 

 

Pin 1 -white (audio?) to a resistor, and another wire I think is the shield

 

pin 2 - 4 jump

 

pin 3 - black (bias?)

 

this seems to match up with fig 5 in lectrosonics wiring diagrams.

 

 

The white is bias and the black is audio. Pin 1 is the ground, Pin 3 is mic level audio and pin 5 is line level.

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Hi Laurence,

 

I've tried to contact you several times about this...left a couple of voicemails and and email and haven't heard back from you. We even tried to contact you over the weekend when we saw your tweet and never heard back from you. It looks like we shipped the reduced sensitivity by mistake. I'd be happy to exchange them for you. I just need you to get back to me so we can arrange the exchange. My email is davef@dvestore.com or you can call me at 360-653-7063. We don't wire these ourselves. We order them from Plus24 already wired. 

 

-Dave Fisk

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The 10k resistor is not correct in any case for any COS-11, be it reduced sensitivity, enhanced sensitivity or ribbed. A 1k resistor is shown in our recommended wiring diagram, This will give you 20 dB more signal which should solve the problem, all ribbing aside. Lectro will send you some tiny 1/10th Watt resistors free of charge if you ask service at 1-800 821-1121. 

Best Regards,

Larry Fisher

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On 10/14/2017 at 7:19 PM, Laurence T said:

Thank you for all your help guys, really appreciate it.

It actually wasn’t from B&H!

Am I right in thinking that if I remove the resistor completely, and attach the white wire straight to pin 5, it will be the correct (and non universal) servo bias wiring?

Yes.

LEF

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  • 2 years later...

This is something i've noticed to - I ordered 4 sets of standard cos's (from a well know UK distributor) two in ta5 and two in 3-pin lemo - going into lectro transmitters. I'm normally an 4060/61 guy, but for continuity with an existing show, I added the above.

 

I've noticed that across the board, I'm running them around 30-36 to get them to modulate properly for normal dialogue - much higher than what I am used to (18-24)

 

is the general consensus that its the resistor thats the culprit?

 

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2 hours ago, craig jackson said:

I've noticed that across the board, I'm running them around 30-36 to get them to modulate properly for normal dialogue - much higher than what I am used to (18-24)

If you are comparing to a different brand mic (4060), the COS-11's might be wired "properly". About the only way to tell is to open the connector and measure (or see) the value of the resistor. Once you have that value, you can decide on a value that gets you to where you want to be. On the other hand, the transmitter is perfectly able to gain up the "missing" 10 dB you speak of and you can just use them as they are.

Best Regards,

Larry Fisher

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  • 9 months later...

So I have 3 Sanken wires, all suppose to be normal sensitivity. I did a test and one came in 10db lower. I sent in the -10db wire with a normal one to a shop to get the -10 to match with the normal wires. They came back matching, except now I have two out of three wires that are -10db...

 

I opened up the connector after reading this thread regarding resistors and wanted to confirm if that was the case.

 

the wires coming under 10db don’t have a resistor and the one “normal” has one.

 

Isn’t a resistor suppose to reduce the sensitivity, not increase? What am I missing?

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There are two correct wirings for a COS-11.

 

https://www.lectrosonics.com/lectrosonics-microphone-wiring/913-uhf-transmitter-5-pin-input-jack-wiring.html?highlight=WyJtaWMiLCJtaWMnIiwibWljJ2VkIiwibWljJ3MiLCJtaWMnZCIsIndpcmluZyIsIid3aXJpbmcnIl0=

 

See Fig 5 (external resistor) and Fig 11(internal resistor) as shown in the above document. You may have two wired as Fig 11 (simpler) and one wired as Fig 5 (harder to do). The difference in gain between a 1k resistor in Fig 5 and the internal 2.7k in Fig 11 is 10 dB. Noise is reduced 10dB also, so gaining up the transmitter by 10 dB does not has zero  ill effects. I always thought the 1k resistor was too low anyway.

Best Regards,

Larry Fisher

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